Matthew Henry Commentary Numbers 21:21-35

"And Israel sent messengers unto Sihon king of the Amorites, saying, Let me pass through thy land: we will not turn aside into field, or into vineyard; we will not drink of the water of the wells: we will go by the king`s highway, until we have passed thy border. And Sihon would not suffer Israel to pass through his border: but Sihon gathered all his people together, and went out against Israel into the wilderness, and came to Jahaz; and he fought against Israel. And Israel smote him with the edge of the sword, and possessed his land from the Arnon unto the Jabbok, even unto the children of Ammon; for the border of the children of Ammon was strong. And Israel took all these cities: and Israel dwelt in all the cities of the Amorites, in Heshbon, and in all the towns thereof. For Heshbon was the city of Sihon the king of the Amorites, who had fought against the former king of Moab, and taken all his land out of his hand, even unto the Arnon. Wherefore they that speak in proverbs say, Come ye to Heshbon; Let the city of Sihon be built and established: For a fire is gone out of Heshbon, A flame from the city of Sihon: It hath devoured Ar of Moab, The lords of the high places of the Arnon. Woe to thee, Moab! Thou art undone, O people of Chemosh: He hath given his sons as fugitives, And his daughters into captivity, Unto Sihon king of the Amorites. We have shot at them; Heshbon is perished even unto Dibon, And we have laid waste even unto Nophah, Which [reacheth] unto Medeba. Thus Israel dwelt in the land of the Amorites. And Moses sent to spy out Jazer; and they took the towns thereof, and drove out the Amorites that were there. And they turned and went up by the way of Bashan: and Og the king of Bashan went out against them, he and all his people, to battle at Edrei. And Jehovah said unto Moses, Fear him not: for I have delivered him into thy hand, and all his people, and his land; and thou shalt do to him as thou didst unto Sihon king of the Amorites, who dwelt at Heshbon. So they smote him, and his sons and all his people, until there was none left him remaining: and they possessed his land." — Numbers 21:21-35 (ASV)

Sihon went with his forces against Israel, from outside his own borders and without provocation, and so brought about his own ruin. The enemies of God's church often perish by the very plans they believe are most wisely devised. Og, king of Bashan, instead of being warned by the fate of his neighbors to make peace with Israel, made war with them, which in the same way proved to be his destruction.

Wicked men do their utmost to secure themselves and their possessions against the judgments of God; but all in vain, when the day of their downfall arrives. God gave Israel success while Moses was with them, so that he could see the beginning of the glorious work, though he would not live to see it finished. This was, comparatively, merely a day of small things, yet it was a foretaste of great things.

We must prepare for fresh conflicts and enemies. We must make no peace or truce with the powers of darkness, nor even negotiate with them; nor should we expect any pause in our contest. But, trusting in God, and obeying his commands, we shall be more than conquerors over every enemy.